Alloy steel



Patented Dec. so, 1938 Qumran sures 1,141,016 my s'mar. retel- Pawn, NewYul-1;, N. r.

Na Application November is, was,

Serial No. 111,616

13 claims. (01. ire-e1 This invention relates to improvements in heat,oxidation and corrosion resisting steels adapted for such uses asvalves, valveseat inserts and related parts 'of internal combustionengines, 5 high speed and other cutting, forming and shearing tools, hotwork dies, die casting dies, and

more generally for use in articles requiring great strength, hardnessand resistance to corrosion, oxidation and scaling at elevated as wellas at atmospheric temperatures.

' This application is a continuation in part 'of my copendingapplication Serial No. 83,451, filed June 4, 1936, which in turn is acontinuation in part of my applications for Letters Patent Nos.

2,009,974 and 2,051,415.

In my patents aforesaid I have described a series of steels, having theproperties above .noted, containing about 18 toi35% chromium, about 1 to10% of metal of the group consisting of nickel 20 and manganese, andabout 1 to 10% or metal of the group consisting of molybdenum, .tungstenand silicon, characterized in undergoing a change in phase or instructure when maintained for a period-usually a matter of hours-atelevated temperature within the approximate range of- 1200 to 1800 F.,whereby they acquire outstanding and distinguishing characteristics ascompared to known steels and also as compared to the characteristics ofthese same steels prior to such heat treatment. Such steels when sotreated acquire high hardness-up to C 65 Rockwel1 or more for someanalyses-as compared to their hardness prior to such heat treatment andfollowing usualrolling, forging or annealing operations.- Elevatedtemperature measurements have shown that these steels actuallyharden atheat, their elevated temperature hardness being superiorto that of knownsteels and their hardv ness on cooling being substantially independentof the rate of cooling. When so hardened these steels undergo nosubstantial reduction in hardness after heating to temperatures as highas 1400" or 1600 F. or even higher for someanalyses, and thisirrespective of the number, duration or temperature of individual heats.

Whereas according to the information of my patentsaforesaid, at leastone of the elements nickel and manganese'and at least one of theelements molybdenum, tungsten and silicon in addition to chromium withinthe percentage limits noted, is required for imparting heat hard=enability, myfurther investigations have established' that straightchrome steels are susceptible to such hardening provided chromium ispresent in sufficient amount, i. e. in excess of about 35%; 5

and also that steels containing about 18 to 35% chromium-and whichare,thereby substantially non-heat hardenable on the basis of theirchromium contents alone, can be rendered so by adding the aboveelementsin the manner taught 10 by my patents aforesaid; or by adding about 1 to10% silicon, about 1 to 10% molybdenum or its equivalent tungsten, orabout 1 to 15% of metal of the group comprising silicon, molybdenum andtungsten, as taught by this application. 15

These latter steels difier from those of'my patents aforesaid in thatmetal of the group consisting of nickel and manganese is not requiredfor imparting heat hardenable properties of such steels.

It is shown in my patents aforesaid that heat 20 'hardenability of thesteels therein described, in-

creases with increasing content of the alloying elements other thancarbon within the limits therein stated. The same is true of the steelsconstituting the subject matter of this applica- 25 tion, as isshown bythe following data:

' Table I I Effect of chromium on hardenability of straigh 30 chromesteels. C 12%; other elements present in usual amounts.

I on Hardnem small 35 Cr r cant pe Alter 10 hrs.

sees

M1811 Effect on .hardenability or adding i"? enable by adding silicon insuflieient amount,

the hardenability increasing with further increase of this element.

Hardness: Rockwell Si per cent Ai'ter 16 hrs.

As rolled at 14000 Steels which contain insuihcient chromium for heathardening, may thus be rendered so hard- Table 11 Effect onhardenability o! adding.molybde- V num to chrome steel. 0 about .14; Crabout 30%; elements other than Mo present in usual Y amounts.

- ments other than Cr, Si,

Hardness: Rockwell 0" Mo per cent After 16 hrs.

As mum at 1400' r.

Heat hardenability may be thus imparted to an otherwise non-heathardenable chrome steel by adding sufficient molybdenum.

Table IV Effect on hardenability of adding molybdenum to chrome-siliconsteels and of adding silicon to chrome-molybdenum steels. C about. .15%;ele- Mo present in usual amounts.

Hardness: Rockwell 0 61 Or Si Mo D61 per per cent cent cent Alter 18hrs.

As rolled at 29.6 3. a 23 45 29. 1 4. 4 27 55 2s. 2 a. 4 4. 7 32 c1 25.2 a. 1 2.4 1 27 41 24. 4 4. 1 2. a a4 45 24. 4 5. 1 1. 7 33 48 29.9 3.11.5 27 51 f 29. c 3. 1 a 5 27 5e 28. 2 3.4 4. 7 32 e1 Comparison of theheat hardening for steel '3 increases with increasing silicon keepingthe chromium and molybdenum about constant.

Similarly the results for steels 'l to 9 inclusive, show thathardenability increases with increasing molybdenum keeping the chromiumand silicon about constant.

Table .v

Effect on hardenability of varying the. chromium content in steelscontaining either or both of silicon and molybdenum. 0 about 15%;elements other than Cr, vSi and Mo present in usual amounts.

Hardness: Rockwell "C" or Mo Art 13 hrs er at 14oo F.

19. 0 5. 6 4. 7 37 44 23. s 3. 7 4. 7 31 52 25. 7 4.3 4.8 30 5e 28. 2 3.4 4 7 32 01 37. 2 1. 8 1. 2 26 63 4o. 7 .9 0 24 e5 Hardenability thusincreases with increasing chromium.

Table VI Effect of carbon onhardenability. Cr about 28.5%; Si about 4%;Mo about 1.7%; elements other than C present in usual amounts.

Hardness: Rockwell "0 0 percent After 16 hrs.

As rolled at F.

Increasing the carbon content therefore does not increase hardenability.

The data of Tables I to VI inclusive, thus establish that: Chromium isthe dominant element as regards hardenability, and if present insumcient amount, 1. e., in excess of about 35%, none of the otherelements above referred to need be present, although additions thereofenhance hardenability. As the chromium content is decreased, otherelements such as silicon, molybde num and tungsten, must be added inincreasing amounts for imparting a given hardenability, additions ofsuch elements being requisite where the chromium is below about 35%. Ingeneral, hardenability increases with increasing additions of theindividual alloying elements other than carto such hardening inappreciable degree. This relationship may be formulated as follows:steels are heat hardenable when the sum comprising two-thirds thechromium content plus twice the silicon content plus the molybdenumcontent divided by twenty-five exceeds unity., Designating this as theHardenability Ratio or more briefly as H. R., this relationship may beexpressed more concisely as follows: (1) For hardenability The datapresented below embracing a wide range of analyses conform to thisrelationship and tend to substantiate it as a rule of generalapplicability to such steels.

. ampliiythose 01 Tables I to V1, inclusive, and

Table VII i Hard- And, my lisrdneas ttockwcii bill Ratio: .42 411011011.11.11. 101100 411400 1 CHROMIUM 10.0 To 20.0 INCLUSIVE 013110141111420.1 To 22.0 INCLUSIVE e 0 .00 20.2 4.0 0 .00 25 20 4 .10 21.0 0.7 01.10 02 40 011110141004 22.1 To 24.0 mcwsrvn CHROMIUM 24.1 m 20.0mowsrva .14 25.0 2.0 0 .04 15 14 .14 24.0 0.0 0. .00 20 20 .14 25.7 4.40 1.04 00 40 .12 25.0 4.0 0 1.05 24 40 .15 24.0 5.4 0 1.10 01 4s .1424.0 1.0 4.0 .02 20 .11 25.7 2.0 1.7 .02 10 1s .12 25.2 0.1 2.4 1.02 2741 .10 24.4 4.1 2.0 1.00 04 45 .10 25.7 4.0 40 1.22 00 50 .14 24.4 5.11.7 1.10 00 4s OHROMIUM 20.1 To 20.0 INCLUSIVE OHROMIUM 20.1 T0 00.0 mclusivn CHROMIUM 00.1 m 00.0 INCLUSIVE CHROMIUM OVER 00.0 55

5 Referring to the data of Table VII, in every instance that thehardenability' ratio is unity or less, the corresponding, steelundergoes little or no increase in hardness after being heat treated;whereas inevery instance that the ratio exceeds unity the hardness ofthe corresponding steel is greatly enhanced by heat treating. Andgenerally speaking, the analyses which are susceptible to the greatestheat hardening are those for which the hardenability ratio is largest.

The data of Table VII embrace a wide range of compositions for steelcontaining chromium both with and without silicon, molybdenum or both;so that the above rule appears to be of general applicability as acriterion of hardenability tor such steels. Ihe data of the table,moreover.

lend further support to the conclusions derived therefrom as abovestated.

"As was the case with the steels of my patents aforesaid, heat hardeningof the steels described herein is a function of time at temperature, and

-in general is more readily secured and to an increased degree if thesteel is in the "as forged" or "as rolled condition before hardening, ascompared to hardening from the as annealed condition, as appears from:

Table VIII Analysis Rockwell "0 Hardness Pre-heat.l1ardened eon-amenTime. hrs. at 1400 F.

C Si Cr M0 .10 0.00 04.00 40101100 25 25 02 42 40 47 1850 F.anneal 20 2020 34 43 45 .12 8.10 25.22 2.43 ASX'OHBd 27 27 28 30 36 42 M l850lianneaL. 24 -25 25 28 29 33 39 As heretofore stated, such steelsafterbeing heat hardened, undergo no substantial reduction in hardnessafter heating to temperatures as high as about 1400 F. or more, as shownby:

Table IX Rockwell C hardness O Si Cr Mo hASt Aft/0r reheating 16 hoursat-- 88 Egg 000 000" 1000 1100* 1200" 1400 F. F. F. F. F. F.

' seats and related parts of internal combustion engines. v ,t

As shown by the data contained in Table VIII,

heat hardening of the steels above described is maintaining the same atele-- vated temperature within the approximate range of 1200 to 1800 F.,until a desired hardening. has been imparted. It is immaterial in thisconnection whether the steel is held within this temperature range whilecooling from some higher temperature, such as that of forging.extruding, etc., or is elevated to temperature 1 within this range fromsome lower temperature for hardening. Also, it is not essential,although preferable, that hardening'be effected at reasonably constanttemperature within the hardening range; the temperature may be permittedto increase, decrease,- or fluctuate during this treatment. All suchmodes of treatment are intends ed to be embraced in the appended claimsby the recital of a steel "characterized in being hardened by heatingwithin the approximate temperature range of 1200 to 1800 F. f

Also reference to molybdenum in the claims is intended to include itsequivalent, tungsten.

Although silicon is classified as a non-metal, or metalloid, by certainauthorities, it nevertheless has the attributes of a metal in the steelsoi.

accomplished by the specification and claims herein.

What I claim is: I

1. An alloy steel, characterized in being hardened by maintaining thesame at temperature within the approximate range of 1200 to.1800 F.until hardened, and in thereafter undergoing no substantial reduction inhardness after heating to any temperature up to about 1400 F., saidsteel containing about 18 to 35% chromium, under 1% of nickel andmanganese, and about 1 to 15% ofmetal of the group consisting of siliconand molybdenum, the balance of said steel consisting principally ofiron.

2. An article subjected to use to elevated temperatures at least aportion of which is made of a steel according to claim 1.

3. A cutting, forming or shearing tool at least a portion of which ismade of a steel according to claim 1.

4. A valve or valve element for internal combustion engines at least aportion of which is made of a steel according to claim 1.

'5. An alloy steel, characterized in being hardened in excess of C 32Rockwell by maintaining the same at temperature within the approximaterange of 1200 to 1800 F. until so hardened, said steel being sohardenable While in the as forged, rolled or annealed condition, theresulting hardness of said steel being substantially independent of therate of cooling from the hardening temperature, and said steelthereafter undergoing no substantial reduction in hardness after-heatingto any temperature up to about 1400" F., said steel containing about 18to 35% chromium, less than 1% of nickel and manganese, and about 1 to15% of metal of the group consisting of silicon and molybdenum, ,thebalance of said steel consisting principally of iron.

6. An alloy steel characterized in being hardened by maintaining thesame at temperature within the approximate range of 1200 to 1800 F.until hardened, and in thereafter undergoing no substantial reduction inhardness after heating to any temperature up to about 1400 F., saidsteel containing: about 18 to 35% chromium, under 1% of nickel andmanganese, and about 1 to 15% silicon, the balance of said steelconsisting principally of iron.

'7. An alloy steel characterized in being hardened by maintaining thesame at temperature within the approximate range of 1200 to 1800 F.until hardened, and in thereafter undergoing no substantial reduction inhardness after heating to any temperature up to about 1400 F., saidsteel containing: about 18 to 35% chromium, under 1% of nickel andmanganese, and about 1 to 15% molybdenum, the balance of Said steeconsisting principally of iron.

8. An alloy steel characterized in being hardened by maintaining thesame at-temperature within the approximate range of 1200 to 1800 F.until hardened, and in thereafter undergoing no substantial reduction inhardness after heating to any temperature up to about 1400 F., saidsteel containing: about18 to 35% chromium, under 1% of nickel andmanganese, and about 1 to 15% of metal of the group consisting ofsilicon and molybdenum, the percentage sum of the molybdenum content,twice the silicon content and two-thirds the chromium content divided bytwenty-five exceeding unity, the balance of said steel consistingprincipally of'iron.

9. A heat hardened alloy steel, hardened by maintaining the sameatelevated temperature within the approximate range of 1200 to 1800 F. andcharacterized in undergoing no substantial reduction in hardness onsubsequent heatingto any temperature up to about 1400 F., said steelcontaining: about 18 to 35% chromium, under 1% of nickel and manganese,and about 1 to 15% of metal of the group consisting of silicon andmolybdenum, the balance of said steel consistingv principally of iro'n.

10. A heat hardened alloy steel, hardened by maintaining the same atelevated temperature within the approximate range of 1200 to 1800" F.and characterized in undergoing no substantial reduction in hardness onsubsequent heating to any temperature up to about 1400" F., said steelhaving a hardness in excess of C 32 Rockwell and containing: about 18 to35% chromium, under 1% of nickel and manganese, and about 1 to 15% ofmetal of the group consisting of silicon and molybdenum, the balance ofsaid steel consisting' principally of iron.

11. A heat hardened alloy steel, hardened by maintaining the same at.elevated temperature within the approximate range of 1200 to 1800" F.and characterized in undergoing no substantial reduction inhardness onsubsequent heating to any temperature up to about1400 F., said steelcontaining: about 18 to 35% chromium, under 1% of nickel and manganese,and about 1 to 15% silicon, the balance of said steel consistingprincipally of iron.

12. A heat hardened alloy steel, hardened'by maintaining the same atelevated temperature within the approximate range of 1200 to 1800 F. andcharacterized in undergoing no substantial reduction in hardness onsubsequentheating to any temperature up to about 1400 F., said steelcontaining: about 18 to=35% chromium, under 1% of nickel and manganese,and about 1 to 15% molybdenum, the balance of said steel consistingprincipally of iron.

13. A heat hardened alloy steel, hardened by maintaining the same atelevated temperature within the approximate range of 1200 to 1800- F.andcharacterized in undergoing no substantial reduction in hardness onsubsequent heating to any temperature up to about 1400 F., said steelcontaining: about 18 to 35% chromium, under 1% of nickel and manganese,and about 1 to 15% of metal of the group consisting of silicon andmolybdenum, the percentage sum of the molybdenum content, twice thesilicon content and two-thirds the chromium content divided bytwenty-five exceeding unity, the balance of said steel consistingprincipally of iron.

PETER. 'PAYSON.

